Submarine sound-signaling apparatus



may u m2@ i f www@ W. HAHNEMANN SUBNARINE SOUND SIGNALING APPARATUS mise. Maren 24. 1921 ,Patented May ll, 1926.

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WALTER HAHNEHANN, 0F KITZEBERG--, NEAR KIEL, GERMANY, ASSIGNOR T0 SIGNAL GESELLSCHAFT M. IB.l H., 0F KIEL, GERMANY.

SUBHABDIE SOUND-SIGNALING APPABATS. Application led March`24, 1921. Serial No. 455,319.

(GRANTED UNDER. THE PROVISIONS 0F THE ACT 0F M ARCH 3, 1921, 41 STAT. L., 1313.)

The invention relates to that group of sound receivers in which the osclllatory system is composed of. two independent osciland elastic members forming an oscillatorystructure is connected with the sound dia-V phragm of such a receiver. For the operation of such apparatus the proper coupling of the two .oscillatory structures with one another is of particular importance. This coupling is dependent on the constructional design of the two structures to be coupled, that is, in the mentioned example, on the design of the sound diaphragm and in particular of the microphone. If, therefore, a different coupling (that is, a closer or looser coupling) 1s to be chosen than that which normally results in the case of a simple connection of two oscillatory structures of given size and design, it is necessary to alter the construction or design of at least one of the two oscillatory structures to be' coupled. Equally it isnecessary, when one of theoscillatory structures is replaced by another of different dimensions', to alter the other of the two oscillatory structures because otherwise a different coupling would resultrthan the one which has been found effective. Let it be assumed that in the course of time, a particular type of microphone has proved especially suitable, which microphone possesses when used with a diaphragm of deiinite size a favourable degrec of coupling. If now, for example. the size of the diaphragm must be altered because it is not strong enough, the relations of the tuning, etc., being otherwise the same, then on using the same tested microphone, with the diaphragm a. diiferent and less favourable degree of coupling is obtained. In order to again obtain the former degree of coupling it is necessary to depart from the tested microphone construction and this departure necessitates a new series of experiments of uncertain length and uncertain result.

The present invention provides a means in such cases of again obtaining the desired favourable degree of coupling, of the oscillatory structures with respect to .one another without altering the construction or design of the oscillatory structures themselves. It consists in connecting the oscillatory structures with one another by means of a lever mechanism of any suitable design.

The invention is represented in diagrammatic form in Figs. 1, 2 and 3. In all these .iigures, a vdiaphragm (the sound radiating member) is shown, which is secured at its periphery to a ring-shaped carrier or holder.

This diaphragm forms part of one oscilserves as the outer mass of one of the vibratory structures, which structure includes also the diaphragm e1 and a portion of the mass m2. The diaphragm serves as the elastic member of this vibratory structure. The diaphragm mass and certain other masses (namely, the mass of water, the fastenlng members of the microphone, and the like) fastened or considered to engage on the centre of thediaphragm, are considered to be combined in the body or mass m2. This body or mass contains also parts which at the same time belong to the microphone, representing the second oscillatory structure. This is represented by the line Z which divides the body m2, by the letter 1' which designates the partbelonging to the said lsecond oscillatory structure (microphone),

and by the letter s which designates the part belonging to the first oscillatory structure (radiating diaphragm). The second oscillatory structure is formed by this portion 1' ofthe mass body m2, by the microphone diaphragm e2 which serves as the. elastic member, and by the other mass ms of the microphone (casing or the like) supported on this microphone diaphragm. It is assumed that the degree of coupling eiifectedI phone to permit it to bend there.

alteration, of course, causes the percentage 1' of the mass in m2 belonging to the second oscillatory structure also to become altered and, since the degree of coupling between the two vibratory structures is determined by the relations of the masses fm,3 to m2, and m, to m2, this alteration results in 'a change in the degree of coupling unless the microphone be altered correspondingly. Since now it is desired that the microphone construction, and therefore the microphone mass 1', remain constant, it is according to the present invention arranged to engage the diaphragm by means of a lever a adapted to transform or change the amplitudes of vibrations passing between the. diaphragm and the microphone. It is possible according to the invention on adjusting the lever to secure the proper ratio of motion transformation, to again obtain the desired degree of coupling in the increasing (Fig. 2) or diminishing sense'(Fig. 3) for every alteration of the radiating structure; because the action of the mass s of the rst osc1llatory structure (the diaphragm) on the mass r of the second (the microphone) varies in direct proportion to the square of the lever transformation, according to the principle which forms the basis of the 1nvention.

The constructional design of the radiating member and the v'detecting' apparatus in no Way limits the scope of use of the invention. The inventive idea can be equally advantageously used with radiating structures of any desired form, and detectors (microphones, telephones and the like) of any desired form. In particular the invention provides a new and easy Way of fulfilling the well-known condition for the efficient operation of such coupled systems in submarine sound receivers, according to which the ratio of the masses m., to m, must be equal to one or less than one.

The manner of construction of the lever system itself does not form the object of the invention, although it is naturally of importance that the lever should be preferably so constructed that its acoustic properties are correct. In this connection it is desirable to avoid the use of ordinary pivots for the fulcrum of the lever. Instead of such pivots the lever itself may be reduced in cross-section at the fulcrumA to such an extent as to enable it to bend at that point. The lever may also be reduced in cross-section at the point of attachment to the micro- The reduced portions are indicated in Figures 2 and 3 at al. At all other'points the lever must be constructed substantially rigid With respect to the frequencies to be employed in the apparatus, and in its entire designl should be preferably particularly light. Care should be taken in calculating such constructions, that the masses of the levers themselves are included in the oscillatory masses, and secondly that the transformation ratio of the lever is calculated according to the above stated rule with this in considera-tion. For example, the portion of the mass m2 in Fig. 3 belonging to the microphone, and the masses of the lever itself (taking into consideration the amplitudes thereof), are included in the calculation of the composite mass which is used in comparison with 4the mass 'm3 in determining the ratio of transformation required from the lever.

I claim:

l. In submarine sound receiving apparatus, two independently vibratory structures, and a lever coupling them together,

-the lever being so connected to the two vibratory structures as to transform the amplitudes of vibrations passing between said structures to an extent dependent upon the percentage of acoustic coupling to be created between the structures.

2. In submarine sound -receiving apparatus, an independently vibratory sound radiating diaphragm, an independently vibratory sound detector, and a lever couplin them together, the lever being so connecte to .the diaphragm/and detector as to transform the amplitudes of vibrations passing between the diaphragm and detector to an extent dependent upon the percentage of acoustic coupling to be created between them.

3. A sound receiving device comprising in combination; a primary vibratory structure including two vibratory masses connected by an elastic sound radiatin member; a second vibratory structure in t e form of a detector having a freely vibratable mass and a second vibratory mass; and a substantially rigid amplitude-transforming lever adapted to unite said second vibratory mass of the detector with a vibratory mass connected to the radiating member; the ratio of the free mass of the detector to the said united masses when the former is multiplied by the square of the ratio of transformation of the said lever, being at most equal to 1.

u '1 4. A sound receiving device compr1s1ng m combination; a primary vibrator structure including an elastic sound radlatlng diaphragm, a vibratory mass attached to the peri'phery of the diaphragm, and a vibrasaid united masses when the former is multiplied bythe square of the ratio of transfortory mass at the center of the diaphragm;

mation of said lever, being at most equal to 1.

5. In sound signaling apparatus comprising a plurality of vibratory structures each including a plurality of masses connected by an elastic member, a lever having a point thereof of relatively-small amplitude of motion connected to one structure and a point of relatively largeamplitu'de of motion oonnected to another structure, the lever being arranged to transform the amplitudes of v1- brations passing betu'een the structures and to effect the degree of coupling between the structures.

6. In sound signaling apparatus comprisinnr a plurality of vibratory structures each including a plurality of masses connected by an elastic member, a lever having a point thereoof of relatively small amplitude of motion connected to a mass of one structure and a point of relatively large amplitude of motion connected to a mass of another structure, the lever being arranged to transform the amplitudes of vibrations passin between the Structures and to effect the egree of coupling between the structures.

7. In sound signaling apparatus comprising a plurality of vibratory structures each including a plurality of masses connected by an elastic member, a lever having a point thereof of relatively small amplitude of motion connected to a mass of one structure and a point of relatively large amplitude ofl motion connected to a mass of another structure, the other mass of the last-named structure being freely vibratalole` the masses connected by the lever forming a composite mass, and the square of the ratio of transformation, of the lever multiplied by the ratio of the freely vibratable mass to the composite mass being at'most equal to 1.

In testimony whereof I aix my signature.

'WALTER HAHNEMANN. 

